The Future of Fuel Efficiency

At the end of August this year, the US Department of Transport's National Highway Traffic Safety Administration (NHTSA) and the US Environmental Protection Agency (EPA) announced new standards to significantly improve the fuel economy of cars and light trucks by 2025. Last week, we took a look at a range of recent engine technologies that car companies have been deploying in aid of better fuel efficiency today. But what about the cars of tomorrow, or next week? What do Detroit, or Stuttgart, or Tokyo have waiting in the wings that will get to the Obama administration's target of 54.5 miles per gallon (mpg) by 2025?

The problem is historic

Ars tackles the future of cars

"The road ahead" is just the second installment in the Ars' three-part series. Last week Jonathan Gitlin tackled innovation in engine design. Next week: alternative methods for manufacturers to create more efficient vehicles. Whatever the technology, it's going to involve gasoline for at least the foreseeable future in the US. Automotive history helps us understand why. Author and journalist LJK Setright told us "we need hardly worry about who invented the motor car." While there are several inventors to whom the first horseless carriages can be attributed, Setright had a point when drawing the starting line through 1885 and Karl Benz's gas-powered three-wheeled machine. Victorian and Edwardian car makers drew on a wide range of fuels and engines. If a man in the street then predicted the next century, it wouldn't have been unreasonable to expect a diverse vehicular landscape. Back then, electric cars were marketed to women as they neither gave off clouds of exhaust nor required someone strong to crank the engine over (the invention of the electric starter motor finished this feature off). By 1900, Thomas Edison was ready to pick this technology as the winner.

Electricity might be making a comeback now, but it was the internal combustion engine—powered either by gas or diesel—that made automobile what it is. Unlike steam, drivers didn't need to stop for heavy fuel to burn or to top up the water for their boilers. Back then, much like today, batteries didn't charge fast enough or contain enough energy to meet most of our needs. But liquid hydrocarbons are cheap and easy to extract, they have good energy density, and don't require high pressure containment. So for over a century, the infrastructure to support the gas-powered car built up across the globe.

Of course, burning hydrocarbons isn't problem-free. They are a finite resource, one we're pulling out of the ground much faster than it took to get down there in the first place. Many of the richest deposits are controlled by autocratic or otherwise unpleasant regimes, upon which another nation might not wish to depend. And then there's the waste problem: nitrogen compounds can cause respiratory disease; lead additives affect development; and the big one, carbon dioxide, drives climate change. Despite these issues, the depth of infrastructure to support the gasoline engine is such that, for the foreseeable future, alternatives like hydrogen or even electricity will remain very niche choices.

The MPG equation

The basics of today's engines may have been put together more than 130 years ago, but that hasn't stopped engineers and scientists from finding new ways to travel further on the same gallon. That benefits drivers who have to pay to fill up their tank, as well as to society at large. It's why governments are using differing approaches to increase fuel efficiency. In Europe, that's mainly via escalating gas taxes, but here in the US we have the Corporate Average Fuel Efficiency (CAFE) regulations.

CAFE was introduced following the oil crisis in 1979 resulting from the Iranian revolution. It started with a modest goal, a mere 18 mpg, something even the Ford Model T was capable of achieving. CAFE increased average fuel efficiency over a number of years, up to 27 mpg in the mid-1980s, but the 1990s saw both oil prices and the idea of the US government exercising regulatory power both drop like stones. There we languished, until rising oil prices and growing sentiment about the need to address climate change intervened (such are the difficulties of making anything happen in Washington, DC). It was actually the car companies that moved first this time around, sensing that parsimonious punters might respond well. DC followed, and in August 2012, the government published new CAFE regulations that will raise average fuel economy to 54.5 mpg by 2025—almost double what they were a mere two years ago (you can find an interesting infographic showing the last 100 years of fuel economy here.)

Now, it's important to note that what CAFE says is a 54.5 mpg car and what the EPA says is a 54.5 mpg car are not really the same thing. For one thing, CAFE standards apply to, and are calculated for, a company's entire product lineup based on a complicated formula. That isn't the same as the simulation of supposedly real-world driving conditions that the EPA uses. What's more, within that product lineup, cars with a smaller footprint (say, a Mini) are expected to get better mileage than larger vehicles (your trucks or SUVs). So, in 2025, a car with a footprint of 41 sq. ft or less will be expected to deliver 61 mpg under CAFE, but only 43 mpg according to the EPA. At the other end of the scale, a truck with a footprint greater than 75 sq. ft only needs a CAFE rating of 30 mpg, or a mere 23 mpg from the EPA. Suddenly it seems like we're not even asking that much!

EPA/NHTSA Fuel Economy standards plus proposals through 2022, based on their published mathematical formulas.

At this point, some of you might be thinking "there are plenty of fuel-efficient cars, but they're all small and on sale in Europe!" Euro car nerds are but a tiny minority within these great United States. Most car buyers, whether they're in Manhattan, New York, or McAllen, Texas, are not going to be lining up for VW Lupos or Renault Twingos—even if they can do 70 mpg. But that's a problem of taste—let's worry about the technology first!

How the magic may happen

The first technology to consider is start-stop. It's arguably a current technology, at least in Europe where I've been hard pressed to rent a car without it. In fact, you could even get a VW Golf equipped with an early system as far back as 1994, but they didn't sell well. Since this is a US-centric site and start-stop is only just beginning to arrive on US roads, it counts.

Start-stop is designed to save gas when it's being most wasted, which is when the engine is running but the car is stationary (i.e. in a traffic jam). Simply, when the car comes to a halt, the engine cuts out. When it's time to move another car length forward, the engine refires and the driver carries on their merry way. One reason for the prevalence of start-stop in European cars, and its late arrival on these shores, is the preference our continental cousins have for manual transmissions. That's because stopping the engine when the car is stationary is the easier part.

As we discussed in part one, car engines are made up of many components with inertia and momentum. This means they can be started quickly, but not instantaneously. It's not so much of a problem with a manual transmission, as selecting first gear from neutral refires the engine (in practice—I've found it's still horribly easy to stall when trying to get moving quickly). But companies like Ford found it wasn't quite that simple with automatic transmissions.

In order to keep the gearbox's hydraulic pressure up, Ford fitted an electric pump. Also, to minimize the delay between the driver wanting to dart into an opening in traffic and the car moving, the transmission is kept in gear instead of dropping to neutral at a stop. "We had to develop some unique control algorithms for the engine and transmission to overcome this obstacle and still ensure an extremely quick, smooth, and quiet restart," said Birgit Sorgenfrei, Ford’s Auto Start-Stop program manager.

And to prevent the nightmare scenario of cars stranded in traffic jams with dead batteries, the control software also monitors the electrical drain on the car (from AC, audio, headlights, etc.) and disables start-stop when necessary. While start-stop doesn't offer much in the way of benefit when it comes to the EPA's fuel efficiency calculations, in city driving, such a system should be able to realize a gas saving of up to 10 percent. Not too shabby, but still not 54.4 in the near-term. Where do engines go from here?

The automotive industry has come up with plenty of ways to increase the efficiency of existing engines. Unfortunately, to reduce fuel consumption and emissions to the low levels of future standards, we can’t just rely on incremental improvements—entirely new kinds of internal combustion engines need to be developed. Fortunately, the research and industrial community has known this for the past few decades. They've been hard at work coming up with these.

Before talking about the new engine concepts, first we’ll dig a little deeper into how traditional engine types work to understand their limitations.

It's tough because the prevailing attitude is "you can pry my V8 from my cold, dead hands". Thank Top Gear for that, I guess.

There is so much to optimize things - shiny new car technology should be last on the list. Walkable, bike-friendly neighbourhoods, bike-friendly cities, a complete change in the current attitude that engine power is equal to dick size and that public transport is socialized evil. Moving freight traffic to a completely separate network. Stop people from driving.

There is so much to optimize things - shiny new car technology should be last on the list. Walkable, bike-friendly neighbourhoods, bike-friendly cities, a complete change in the current attitude that engine power is equal to dick size and that public transport is socialized evil. Moving freight traffic to a completely separate network. Stop people from driving.

-Then- start thinking about engines.

It doesn't have to be an either-or proposition. My city is finally getting the notion that sidewalks and bike paths are really cool and nifty and when they put them in they get a ton of use, so any new roads or modifications get the pedestrian treatment. Unfortunately, rebuilding roads and cities takes a lot of time and huge amounts of money. I'm getting a sidewalk on my nearest main street in 15 years, and we're the lucky ones since we're actually on the schedule. The average household here is going to buy 2 or 3 cars in that amount of time.

The car isn't going away any time soon -- probably not this century. Ignoring improving the car because you wish people didn't have to use them isn't really a very effective use of those intervening decades.

"In both engines, the high temperatures leading to NOX production are mostly caused by burning of near-stoichiometric mixtures: gasoline engines only operate at this ratio, and in diesel engines there are regions where the fuel and air can mix and burn completely."

Any lean spray combustion system where the burned gas termperature is much higher than the boiling point of the fuel that does not allow for premix will have a flame front at stoichiometric conditions regardless of how lean the overall mixture is - and this is the best-case condition. Each individual droplet has a flame around it where oxygen and fuel is consumed by the flame. This deficit drives diffusion of both from different directions until the flame's location happens to park where the fuel consumed balances the oxygen consumed (stoichiometric). If you're in a locally rich zone the flame will encompass a cloud of drops. Each individual drop will partially burn in an oxygen-starved region creating unburned hydrocarbons, carbon monoxide, etc. If these burn out later that's great. However, the combustion is often quenched and these products go right out the exhaust.

Both port fuel injection and gasoline direct injection have mixing before the spark occurs. Ideally, such systems would not have to reach the high peak temperatures associated with stoichiometric combustion. However, that benefit can only be realized if we could run the darned things lean.

The other option is to rely on exhaust gas recirculation (which is mentioned in the article). The burned gases become inert compounds that, like nitrogen don't participate in the combustion they just suck up thermal energy. That lower the peak temperature without leaving any oxygen around to ruin the catalysts.

Until Americans get over their pre-occupation with 'yank tanks' then the vendors will keep producing gas guzzling cars for the 'Honey Boo Boo' folk of heart land America whether us 'snooty types' like it or not. Cold hard reality is that things have to get a lot worse to the point of absolute crisis before the Joe and Jane Sixpack pull their head out of their ass to make sound long term purchasing decisions.

It's tough because the prevailing attitude is "you can pry my V8 from my cold, dead hands". Thank Top Gear for that, I guess.

There is so much to optimize things - shiny new car technology should be last on the list. Walkable, bike-friendly neighbourhoods, bike-friendly cities, a complete change in the current attitude that engine power is equal to dick size and that public transport is socialized evil. Moving freight traffic to a completely separate network. Stop people from driving.

-Then- start thinking about engines.

Full disclosure - I've got a naturally aspirated tuned up(and down in economy mode) V6 in my Audi,so .. I'm nominally one of the 'Top Gear' crowd.Anyway,regarding the ideas - Yes,making areas a bit more bike-friendly (preferably by completely isolating bikes from the rest of the traffic) is a great idea that should help out at least for short commutes. Another thing that can be done is to teach people to drive efficiently - no offense,but if someone is doing more than 2.2-2.4k RPM in an urban environment might as well pour petrol in a can and light it on fire for all the good it's doing. Another thing people ought to get through their sculls is that less dynamic driving = less fuel use. The oh-so beloved darting from traffic light to traffic light again doesn't help at all. And finally,the most overlooked thing of all (at least going by observations of my friends in the US) - walk goddamnit. You want to pop by a shop for a coffee or something, WALK. Odds are you'll be there in about the same amount of time,plus the exercise won't kill you

'How we'll get to 54.5 mpg by 2025'... yes you certainly do mean the 'we in the US'.

My Ford Fiesta did a respectable 60mpg (US gallons). My friend who had a longer commute bought a Toyota Aygo which could do an incredible 80!

The only component you need to upgrade is the one between your ears. No magic technological breakthroughs required.

I don't get the "wah wah wah this is so US-centric" complaints that this and the previous article have generated. Do none of you notice the fact that any time a price is mentioned the denomination is in dollars? That the data format is American? Or the spelling? Maybe this paragraph should have given it away:

"At this point, some of you might be thinking "there are plenty of fuel-efficient cars, but they're all small and on sale in Europe!" Euro car nerds are but a tiny minority within these great United States. Most car buyers, whether they're in Manhattan, New York, or McAllen, Texas, are not going to be lining up for VW Lupos or Renault Twingos—even if they can do 70 mpg. But that's a problem of taste—let's worry about the technology first!"

I think conserving fuel with our current technologies is and will continue to be done by many small actions (i.e. "death by a thousand cuts"). One thing that has always irritated me with regards to fuel consumption is stop lights. So much wasted by not making more effort to "time" the lights (such as, coordinate the stop lights in a manner that one travelling along at near the speed limit for a particular road will catch green lights). I understand this can't be done everywhere, but it is still underutilized in my neck of the woods. Particularly irritating is when interstate entrances with stop lights aren't timed. There is no reason for that, as there is no "scheduled" stop for the interstate, itself. There also some people who've brought up safety issues when I discuss this - mostly to the effect of "red lights make people slow down". However, if you time the greens to the speed limit, you will reward those who are driving the prescribed limit with less waiting.

At any rate, just a small measure, but many small measures could add up. The more start/stop comes into usage, the less this problem will be, anyway. At 100% market saturation of start/stop, the only fuel consumption issue this would help is with regards to re-accelerating to the cruising speed.

It's tough because the prevailing attitude is "you can pry my V8 from my cold, dead hands". Thank Top Gear for that, I guess.

There is so much to optimize things - shiny new car technology should be last on the list. Walkable, bike-friendly neighbourhoods, bike-friendly cities, a complete change in the current attitude that engine power is equal to dick size and that public transport is socialized evil. Moving freight traffic to a completely separate network. Stop people from driving.

-Then- start thinking about engines.

The two are not mutually exclusive. If BMW can do it with its new M5, then so can everyone else

I have no comments on fuel economy; the U.S. is abysmally far behind continental Europe in both efficiency and standards, so this effort isn't actually going to take any more effort than convincing Americans that high efficiency vehicles can still be sporty and re-restricting "light trucks" as commercial (requiring an additional step in licensing in most states that basically assures the state that you will be using the vehicle for legitimate business) and getting on with things.

However, the idea that getting up to speed quickly with a stick is hard, Jonathan, is just demonstrative of a lack of incentive to learn how to do so because you don't drive a manual transmission daily.

I'm still of the opinion that you shouldn't be licensed to use automatics if you can't pass the driving test with a manual.

I have no comments on fuel economy; the U.S. is abysmally far behind continental Europe in both efficiency and standards, so this effort isn't actually going to take any more effort than convincing Americans that high efficiency vehicles can still be sporty and re-restricting "light trucks" as commercial (requiring an additional step in licensing in most states that basically assures the state that you will be using the vehicle for legitimate business) and getting on with things.

However, the idea that getting up to speed quickly with a stick is hard, Jonathan, is just demonstrative of a lack of incentive to learn how to do so because you don't drive a manual transmission daily.

I'm still of the opinion that you shouldn't be licensed to use automatics if you can't pass the driving test with a manual.

Not to mention that acceleration using a semi-automatic gearbox or especially a manual one is actually faster.. Or the fact that driving stick gives you more control over a variety of circumstances (ie - driving on snow and ice). Or the fact that stick IS more economic,because you can drive at the RPMs and gear you want to use that's best for the road conditions and not the middle of the road CPU logic in the automatics

It's tough because the prevailing attitude is "you can pry my V8 from my cold, dead hands". Thank Top Gear for that, I guess.

There is so much to optimize things - shiny new car technology should be last on the list. Walkable, bike-friendly neighbourhoods, bike-friendly cities, a complete change in the current attitude that engine power is equal to dick size and that public transport is socialized evil. Moving freight traffic to a completely separate network. Stop people from driving.

-Then- start thinking about engines.

Moving freight to another network would be awesome... except that we let that network (rail) deteriorate so badly that it would take quite a bit of money and effort to revitalize it to the point of usefulness again.

Biking does seem to be coming into vogue again. In my hometown they've been adding them left and right for the last few years - partially in an effort to impress the rest of the country during a high profile sporting event last year (Super Bowl). Of course, I would be wary of using most of these new bike lanes, as they are really just lines painted on the road.

Personally, I ride my motorcycle as much as possible to save on gas. There are a lot of arguments against doing this (both for safety and costs). However, I find the cost complaint is somewhat negated when you pay cash (particularly for a used bike). As for safety - well, I guess I have to die of something (to steal an old smoker's line).

Ars should have funded a fact finding expedition to Ferrari (maybe Maserati?) to see how they plan to implement this.

I don't think Ferrari or Maserati have much to worry about. I believe the average MPG is calculated so that it includes all cars in the company. And Ferrari and MAserate are owned by Fiat, which makes mostly small cars with excellent MPG. So few GT's or supercars in the mix wont affect the fleet-wide MPG all that much.

The legislation is fundamentally flawed by trying to force too much detail. The sliding scale based on footprint is ridiculous and says a small car getting 30mpg is more of a problem than a truck getting 20mpg. The fact is, people will need to drive smaller cars to improve fleet mileage. Replacing today's 15mpg vehicles with 30mpg vehicles has much more value than replacing the 30mpg vehicles with 60mpg vehicles, due to both the diminishing returns as mileage improves and the vast percentage of our fleet made up of light trucks/SUV's.

Ars should have funded a fact finding expedition to Ferrari (maybe Maserati?) to see how they plan to implement this.

I don't think Ferrari or Maserati have much to worry about. I believe the average MPG is calculated so that it includes all cars in the company. And Ferrari and MAserate are owned by Fiat, which makes mostly small cars with excellent MPG. So few GT's or supercars in the mix wont affect the fleet-wide MPG all that much.

Is fuel economy calculated by company as an average? If so, that would leave some extreme outliers.

I have no comments on fuel economy; the U.S. is abysmally far behind continental Europe in both efficiency and standards, so this effort isn't actually going to take any more effort than convincing Americans that high efficiency vehicles can still be sporty and re-restricting "light trucks" as commercial (requiring an additional step in licensing in most states that basically assures the state that you will be using the vehicle for legitimate business) and getting on with things.

However, the idea that getting up to speed quickly with a stick is hard, Jonathan, is just demonstrative of a lack of incentive to learn how to do so because you don't drive a manual transmission daily.

I'm still of the opinion that you shouldn't be licensed to use automatics if you can't pass the driving test with a manual.

Not to mention that acceleration using a semi-automatic gearbox or especially a manual one is actually faster.. Or the fact that driving stick gives you more control over a variety of circumstances (ie - driving on snow and ice). Or the fact that stick IS more economic,because you can drive at the RPMs and gear you want to use that's best for the road conditions and not the middle of the road CPU logic in the automatics

The real issue is that driving stick is not compatible with the way Americans drive, which is with a phone in one hand and a donut in the other.

The fact that CAFE standards are somehow politically inflated over the real-world EPA mpg requirements does make it seem like it will be marginally easier to hit the 54mpg target, but don't be fooled - tweaking the engines of present day cars and trucks is not going to cut it.

Cars will simply have to be smaller, lighter and have less power than they do today. Most will also have to incorporate expensive hybrid technology, as when operating in electric mode they get an EPA "mpg" rating that does not take in to account electrical generation and transmission inefficiencies. Yep, the entire game is rigged towards electric, based on the fantasy that some day we'll all be recharging our cars using our own personal 100kW solar array, when if fact, in 2025, most electricity will still come from hydrocarbons, and will be delivered over the grid.

Moving freight to another network would be awesome... except that we let that network (rail) deteriorate so badly that it would take quite a bit of money and effort to revitalize it to the point of usefulness again.

??? The plurality of freight miles in the U.S. is rail. The U.S. freight rail system is the envy of most nations.

There's a lot of uninformed commentary in the comments today, much of it of the anti-U.S. type.

Quote:

Personally, I ride my motorcycle as much as possible to save on gas. There are a lot of arguments against doing this (both for safety and costs). However, I find the cost complaint is somewhat negated when you pay cash (particularly for a used bike). As for safety - well, I guess I have to die of something (to steal an old smoker's line).

Surprisingly, most older motorcycles, especially of the carbuerated type, get pretty mediocre fuel mileage, not much better than a new subcompact - and manage to pollute a lot more while doing so, due to far cruder (or nonexistent, typically) emissions controls. They are cheaper, though, but really very dangerous and of limited usefulness in locations that have winter.

I want to know the real answer as to why Americans aren't offered more, small, TDI engines RIGHT NOW.

Most cars in the US have diesel counterparts everywhere else in the world. It isn't a matter of building new tech. It isn't a matter of redesigning the wheel (pun intended). Just switch the driver controls to the left side of the car and be done with it.

Doing so would boost most passenger cars to around 40MPG immediately. SUVs and minivans would probably be around 30MPG. Again, this is without doing anything else!

It's tough because the prevailing attitude is "you can pry my V8 from my cold, dead hands". Thank Top Gear for that, I guess.

There is so much to optimize things - shiny new car technology should be last on the list. Walkable, bike-friendly neighbourhoods, bike-friendly cities, a complete change in the current attitude that engine power is equal to dick size and that public transport is socialized evil. Moving freight traffic to a completely separate network. Stop people from driving.

I think conserving fuel with our current technologies is and will continue to be done by many small actions (i.e. "death by a thousand cuts"). One thing that has always irritated me with regards to fuel consumption is stop lights. So much wasted by not making more effort to "time" the lights (such as, coordinate the stop lights in a manner that one travelling along at near the speed limit for a particular road will catch green lights). I understand this can't be done everywhere, but it is still underutilized in my neck of the woods. Particularly irritating is when interstate entrances with stop lights aren't timed. There is no reason for that, as there is no "scheduled" stop for the interstate, itself. There also some people who've brought up safety issues when I discuss this - mostly to the effect of "red lights make people slow down". However, if you time the greens to the speed limit, you will reward those who are driving the prescribed limit with less waiting.

At any rate, just a small measure, but many small measures could add up. The more start/stop comes into usage, the less this problem will be, anyway. At 100% market saturation of start/stop, the only fuel consumption issue this would help is with regards to re-accelerating to the cruising speed.

Ars should have funded a fact finding expedition to Ferrari (maybe Maserati?) to see how they plan to implement this.

Yeah, Because the most popular vehicles (you know, the ones that contribute the most to air pollution) are obviously Maserati's and Ferrari's. :\

Instead of being snarky, how about addressing the article and issue at hand.

I'm all for increased fuel economy in general. However, there are also other ways to reduce pollution by vehicles. Going electric, hydrogen fuel cells, alternative combustible fuels, better mass transportation, better city design etc...

There's more than one way to skin a cat. As such, let's go at this issue from all fronts, rather than just fuel economy alone. And lets leave the snark out of this, as this is an issue that affects us all. An issue that hits us in terms of pollution, use of finite resources, and economically.

Actually, seeing what their (and Porsche, Lamborghini, Pagani, and ...) plans to increase fuel economy in their market segment *would* be interesting to me. Seeing as their market segment really does push edges of performance. The difference in approach may be quite different, as compared to the econo-box.

The real issue is that driving stick is not compatible with the way Americans drive, which is with a phone in one hand and a donut in the other.(I learned on stick, but switched to automatic years later.)

Well,that's a bit harsh... On the other hand,the whole 'learning to drive stick' thing can be used as a litmus test if someone is cut out to be a driver or not. No offense, but if someone can't grasp the basics of manual gearboxes and starting to apply 'em with a couple of hours on a practice track,he/she doesn't belong on the road,where him/her would have to deal with a hell of a lot more than to remember the 'reach/maintain RPM - press the clutch - shift up or down(depending on the RPMs) - release the clutch'